The fusion of an electron with a proton is a process known as electron capture. Electron capture occurs when an electron is absorbed by a proton in the nucleus, resulting in the conversion of the proton into a neutron. This process is governed by the weak nuclear force.
During electron capture, the electron combines with a proton to form a neutron and an electron neutrino:
p + e⁻ → n + νₑ
The resulting neutron remains in the nucleus, and the neutrino carries away the excess energy and other properties. Electron capture typically occurs in situations where the proton-to-neutron ratio is not optimal for stability, such as in certain isotopes of elements.
As for radioactivity, electron capture itself is not a radioactive process. It is a nuclear transformation that can occur naturally in some isotopes. However, isotopes that undergo electron capture often have other radioactive decay modes as well. Electron capture can be an alternative decay pathway for unstable isotopes, allowing them to transition to a more stable state.
In such cases, electron capture is considered a type of radioactive decay because the nucleus of the atom is changing. The resulting nucleus may be in an excited state, and it may subsequently release gamma radiation or undergo additional radioactive decay modes (such as beta decay) to reach a more stable configuration.
So, while electron capture itself is not inherently radioactive, it can be associated with radioactive decay processes depending on the specific isotope and its nuclear properties.